Knife gate valves are well known in the art for use in a variety of applications in a broad range of industries, including but not limited to, pulp & paper, chemical, petroleum refining, mining, iron and steel manufacture, waste water, power generation, food and beverage, and marine applications. In particular, knife gate valves are advantageous for use in non-abrasive and abrasive slurry applications and for large diameter water applications. The use of elastomeric valve seats are known to be particularly helpful for applications having high solids or prone to scaling.
One advantage of knife gate valves is the ability to cut through slurries, scale, and surface build ups. Another advantage is the unobstructed flow path, which not only provides high flow capacity, but also allows large objects to safely pass through the valve. Small face-to-face dimensions reduce the weight of the valve and facilitate piping design. Knife gate valves are typically available in sizes as small as 2″ diameter to specially fabricated valves exceeding 100″ in diameter.
Disadvantages of knife gate valves historically have been a general inability to provide a tight shut off and the presence of cavities within the valve that promote contamination of the fluid stream. The use of elastomeric gate seals has increased the ability of knife gate valves to provide a tighter shut off, but other concerns remain. U.S. Pat. Ser. No. 10/425,226, incorporated herein by reference, filed Apr. 29, 2003 by the common assignee of the present application and listing common co-inventors Vanderberg and Reeves, discloses a lateral seal for use in the stuffing box of the chest seal of a knife gate valve, wherein the lateral seal is adapted to receive an injectable packing material to improve the sealing relationship.
While this design improves the sealing relationship, this design allows the injectable packing material used in the lateral seal to mix with the fluid media, which can be disadvantageous in some applications. Accordingly, improving the seal structures of knife gate valves is a continued goal of valve manufacturers.